In his criticism of the leading pro-Leave campaigner and Tory leadership favourite, Lord Dubs highlighted Mr Johnson’s warning that Turkey was about to join the EU.

The issue of the country’s likely accession to the bloc was deeply divisive during the referendum, with the Brexit camp accused of “scaremongering” after it claimed Turkish membership would lead to an influx of criminals to the UK, while also putting public services under pressure.

Lord Dubs, a former child refugee who escaped the Nazis by the Kindertransport, told peers that since the “wonderful days” of the London Olympics the UK had become “small, inward-looking and mean-minded”.

He said: “If ever the country needed leadership to tackle hate crime, leadership to condemn those awful people in our society who are taking advantage of minorities in this country, if ever there was time for leadership it is now.”

Lord Dubs added: “I am dismayed that someone who wants to be Prime Minister of this country peddled racial hatred, peddled opposition to migration by saying millions of Turks were going to come to this country.

“And after the referendum he then says it wasn’t about immigration at all.

“Anybody who knocked on doorsteps knows there was one issue that won the referendum for the Leave campaign and that was immigration.

“It was the immigration argument that did it and the hate crime is a result of that immigration argument.”

Opposition spokesman Lord Rosser pointed to reports of racial abuse and attacks following the EU vote.

He said: “All this was unleashed by the campaigning during, and outcome of, a referendum that was called not in the national interest but because of splits in the Conservative Party.

“The result of the referendum has emboldened those with feelings of such hatred, because in the light of the tenor of much of the campaign and its concentration on migration, such people now feel that the result has been an indication of support for their abhorrent views, and has given those abhorrent views a level of respectability that they did not have before.”